Brake control valve



Jan. 18, 1944. P Rn-TENDEN 2,339,380

RAKE CONTROL VALVE Filed April 28, 1942 INVENTOR ATTO R N EY Patented Jan. 18, 1944 BRAKE CONTROL VALVE Philip L. Crittenden, Edgewood, Pa., assignor to The Westinghouse Air Brake Company, Wilmerding, Pa., a corporation of Pennsylvania Application April 28, 1942, Serial No. 440,767

1i) Claims.

This invention relates to fluid pressure brakes and more particularly to the automatic type operative upon a reduction in brake pipe pressure t eiect an.application of brakes.

In Patent No. 2,031,213 issued to Clyde C. Farmer on February 18, 1936, there is disclosed a fluid pressure brake equipment embodying a brake controlling valve device which comprises a service portion and an emergency portion both of which are controlled from a brake pipe. The service portion is operative upon a service reduction in brake pipe pressure to eiect a service application of brakes while both portions are operative upon an emergency reduction in brake pipe pressure to effect an emergency application of the brakes.

The emergency portion comprises a piston subject to the opposing pressures of the brake pipe and a quick action chamber, and said piston is arranged to be operated by a differential produced between said pressures upon a service rate of reduction in brake pipe pressure to move an auxiliary slide valve relative to a main slide valve to a service position. In service position of the auxiliary slide valve a communication is opened for venting iluid under pressure from the quick action chamber at the same rate as the brake pipe pressure is reduced, so as to thereby prevent further movement of these parts upon a service reduction in brake pipe pressure. The communication through which fluid under pressure is vented from the quick action chamber in service position of the auxiliary slide valve is so restricted however that the pressure in said chamber cannot reduce as fast as the brakepipe pressure reduces upon an emergency rate of reduction in brake pipe pressure, in Which case a sufcient differential of pressures is attained on the piston to move same and the auxiliary slide valve relative to the main slide valve past the service position to an emergency position in which fluid under pressure is supplied from the quick action chamber to a brake pipe vent valve device for actuating same to eiect a sudden local emergency reduction in brake pipe pressure for propagating the emergency action serially throughout a train. The emergency piston is also responsive to this emergency reduction in brake pipe pressure to move the main slide valve to a position for supplying fluid under pressure to a brake cylinder device for applying the brakes.\

The emergency piston and auxiliary slide valve are so designed as to normally require about vetenths of a pound per square inch diierential between the pressures in the brake pipe and quick action chamber to move same to their service positions. A stabilizing spring associated with the piston is arranged to come into action about the time the auxiliary slide valve reaches service position to oppose movement of said piston and slide valve past service position. A differential between the-pressures in the brake pipe and quick action chamber of about seven-tenths ofv a pound per square inch on the emergency piston is required to overcome this spring. Thus the brake pipe pressure must be reduced about one and two-tenths pounds per square inch below that in the quick action chamber in order to provide a sufcient differential on the emergency piston for moving said piston and the auxiliary slide valve past service position. The stabilizing spring therefore acts in conjunction with the quick action chamber vent in service position of the auxiliary slide valve to stabilize the piston and auxiliary slide valve against movement past service position to thus prevent an undesired emergency application of the brakes upon a service reduction in brake pipe pressure.

After an emergency valve device has been in use, it is possible that the static resistance to movement of the piston and auxiliary slide valve may become increased due to accumulations of foreign matter, lack of lubricant, use of improper lubricants, or for some other reason, and as a result a diierential of pressures exceeding the fivetenths pound per square inch above mentioned might be required to start the piston and auxil iary slide valve moving toward service position upon a service reduction in, brake pipe pressure. This is not liable to result in any undesired operation if the kinetic resistance to movement of these parts also increases suiiciently and as long as the differential in pressures required to start the parts moving does not exceed the one and two-tenths pounds above mentioned. However, if the kinetic resistance to movement of these parts remains suiciently low when a relatively high diierential is required to overcome static resistance, then after the parts start moving, the movement may be so sudden that suiiicient inertia may be developed as to move the parts through service position to emergency position against the opposing action of `the stabilizing spring and the effect of the venting of fluid under pressure from the quick action chamber in service position. If this should occur then an undesired emergency application of brakes will result from a service reduction in brake pipe pressure.

The principal object of the invention is therefore the provision of means for insuring intended operation of an emergency valve device upon a service reduction in brake pipe pressure even though the static resistance to movement f the emergency piston and auxiliary slide valve may become undesirably increased as above described.

Other objectsA and advantages will be apparent from the following more detailed description of the invention.

In the accompanying drawing the single iigure is a diagrammatic view, mainly in section, of a portion of a iiuid pressure brake equipment em bodying the invention.

The portion of the brake equipment shown in the drawing is substantially thesame as disclosed in the aforementioned patent, in View of which the following descriptionA of parts and operation will -be limited only tothat deemed necessary to a comprehensive understanding of the invention.

As shown in the drawing, the brake equipment comprises a pipe bracketl I having one face upon which is mounted an emergency valve device 2 and having another face (not shown) for carrying a service application valve device (not shown) and which forms no part of the invention. Connected to another` face of the pipe bracket are the following pipes:

Pipe 3 for connection with an auxiliary reservoir (not shown), pipe 4 for connection with a brake cylinder pressure retaining valve device (not shown), pipe 5 leading to an emergency reservoir 6, pipe 'i leading to a brakev cylinder device r8, and pipe 9 which is connected to a brake pipe I0.`

The emergency valve device 2 comprises a casing containing an emergency piston II having at one side a chamber I2 connected to the brake pipe IIJ by way of passages I3, I4, and pipe 9, andhaving at the opposite side a valve chamber I5 communicating with a quick action chamber I6 through a passage II.

The valve chamber I5 contains a main slide valveV I8 and an auxiliary slide valve I9 mounted on `and adapted to move relative to the main slide valve Il. The piston Il is provided with a stem 20 having a recess in which the auxiliary slideW valve I9 is disposed for movement with the piston. The main slide valve I8 is loosely disposed between a shoulder 2I formed on the back nof piston Il and a shoulder 22 provided on the end of the stemkZl, and is arranged to be moved by engagement with one or the other of said shoulders according to the direction of movement of the piston. Y

Aplunger 23 is slidably mounted in a suitable bore provided in the end of piston stem 2i] and has a guide stem 'I5 which slidably extends through a bore provided in a nut 'I6 closing the end of the bore in said stem. A spring 24 is interposed between the nut 'I6 and plunger 23 and acts to urge said plunger into engagement with a shoulder 25'formed in the stem. This shoulder is so located that when the plunger 23 engages same, the outer face of the plunger is beyond the shoulder 22 but spaced from the end' of the main slide valve I8 with these parts in their normal position shown in the drawing. l

A removable cover `26 is secured to the emergency valve casing over the left-hand end ci valve *chamber I5. rihis cover is'provided with a bore in axial alignment with the piston II and in which the cylindrical end of thepiston stem 20 is slidably mounted. A cylindrical recess is provided: in the cover 26k around the portion in which the end of the piston stem is mounted. This recess is of larger diameter than that of valve chamber I5 so as to provide a shoulder 21 on the casing. A movable stop 28 is slidably mounted in this recess and urged against shoulder 27 by a spring 29 also contained in said recess and interposed between said stop and the end wall of the recess.

The stop 2B is provided with an axial opening through which the end of the piston stem 20 freely extends and said stem has an annular collar 30 arranged to engage the stop 28 on the side opposite that engaged by spring 29. The

'main slide valve I8 is provided with a rearwardly extending nger 3l for engaging the stop 2B. This engagement of the piston stem 29 and slide valve I8 with the stop 28 defines the normal positions of said piston and slide valve. The valve chamber II and the chamber at the left-hand side of the stop 28 are in constant communication through an opening 32.

A rocking pin 35 is interposed between one face of a flexible diaphragm 35' and the main slide valve I8'and is subject to the pressure of a spring 31 and of a fluid in a chamberf which is supplied with fluid under pressure from the emergency reservoir S by way of pipe 5 and passages 39 and 4U. In practice, these pressures applied to the rocker pin 35 are transmitted to the main slide valve i8, when the emergency valve chamber I5 is vented, for holding the main slide valve seated against the pressure of iiuid acting on its seating face as will be hereinafter brought out.

Associated with the emergency valve device is a brake pipe vent valve device comprising a piston 4I and a vent valve 42 operatively connected to said piston by means of a stem 43. The vent valve 42 is contained in a chamber 44 which is in constant communication with the brake pipe I0 through passages 45, 46, I3 and I. A spring 41 in chamber 44 acts on the vent valve 42 for urging same into engagement with a seat rib 48 to close communication from chamber 44 to chamber 49 which is open to the atmosphere through a passage 50.

The vent valve piston 4I has at one side a chamber 5l connected by a passage 52 to the seat of the main slide valve I8, and has at the opposite side a chamber 53 open to the atmosphere through chamber 49 and passage 50. A blow-down timing port 54 through the piston 4I connects chambers 5I and 53 while a leakage groove 55 provided in the wall of the piston bore also connects said chambers when said piston is in its normal position, as shown in the drawing.

The operation of the parts of the brake equipment so far described is as follows:

When the brake pipe Ii] is charged with iiuid under pressure, uid under pressure flows therefrom through pipe 9 and passage I4 to passage I3 from whence it flows in a direction toward the left-hand to the emergency piston chamber I2 and in the opposite direction to the service portion (not shown) of the equipment.

The service portion of the equipment is a1'- ranged to operate upon an increase in pressure in brake pipe I to supply uid under pressure to the emergency reservo-ir S for charging same and to establish communication through which fluid under pressure is released from the brake cylinder device 8 for releasing the brakes, and is also operative upon both a service and an emergency reduction in pressure in brake pipe IB to supply uid under pressure from the auxiliary reservoir (not shown) to a passage 56 and thence to brake cylinder device8 for applying the brakes in the same manner as described in' the .aforementioned patent, which operation however is not pertinent to the invention.

With the parts of the emergency valve device 2 in the normal position, as shown in the drawing, fluid under pressure suppliedto piston chamber I2 upon an increase in pressure in the brake pipe Iii flows through a restricted feed port l to passage I? and thence to the emergency valve chamber l5 and quick action chamber I5 for charging said chambers with uid at brake pipe pressure.

With the parts of the emergency valve device in their normal position shown in the drawing, passage 52 which leads to the vent valve ,piston chamber 5I is lapped by the main slide valve I 8. The piston chamber 5I being open to the atmosphere through port 54 and leakage groove 55 is therefore at atmospheric pressure which permits spring 4l to seat the vent valve 42 against seat rib 48. With the vent valve 42 seated, the vent valve chamber 44 is charged with iiuid supplied from the brake pipe Iii through passages I4, I3, 45 and 45.

When a service reduction in brake pipe pressure is eilected to effect a service application of brakes, a corresponding reduction in pressure occurs in the emergency piston chamber I2. Fluid under pressure then tends to ow back from valve chamber I5 and quick action chamber I6 through the feed port 5l to the piston chamber i2, but this feed port is so restricted that a diierential of pressures develops on the opposite sides of the piston Il upon a service reduction in brake pipe pressure.

When this differential increases to a certain degree, such for example as five-tenths of a pound per square inch, the piston I I, assuming its frictional condition and that of auxiliary slide valve I9 to be normal, moves toward the righthand and shifts the auxiliary slide valve to service position in which a service port 58 in the auxiliary slide valve registers with a port 5d in the main slide valve IS, which port 59 registers with an atmospheric passage 6a. Through this communicatio-n, iiuid under pressure is then vented from the valve chamber l5 and quick action chamber at a rate corresponding to the service rate of reduction in brake pipe pressure effective in piston chamber I2 so as to thereby limit the pressure differential on the piston I I, to such a degree as to prevent movement of these parts past service position. Moreover, in service posil tion of the auxiliary slide valve, the plunger 23 engages the end vof the main slide valve I8 so that further movement of the piston I5, that is in the direction of the right-hand past service position, is opposed by the pressure ofk spring 24 acting on said plunger.

The spring 24 is provided to act in conjunction with the service venting of iiuid under pressure from the quick action chamber I6 through ports 58 vand 59 to prevent movement 'of the emergency piston l! and auxiliary slide valve I9 past the service position upon a service reduction in brake pipe pressure and this is normally accomplished since the spring 24 is so designed as to require an increase in the pressure differential on the piston of for instance seven-tenths of a pound per square inch, to overcome the spring so that the piston may continue to move. By means of the service venting of fluid under pressure from the valve chamber I5 and `this stabilizing action of spring 24, movement of the emergency valve piston and auxiliary slide valve past service position upon a service reduction in brake pipe pressure is therefore prevented when the frictional characteristics of the piston and auxiliary slide valve are of a substantially normal value.

When an emergency reduction in brake pipe Apressure is eiiected, the rate of reduction in pressure in piston chamber I2 lso exceeds the restricted venting capacity of service ports 58 and 5S to reduce the pressure in valve chamber II and quick action chamber i8, that the differential of pressures on the emergency piston II promptly increases sufficiently to overcome the pressure of the stabilizing spring 24 whereupon said piston moves the auxiliary slide valve I9 further relative to the main slide valve I8 to an emergency position which is deiined by engagement of shoulder 22 on the piston stem 2i] with the lefthand end of the main slide valve i8.

1n emergency position of the auxiliary slide valve I9, a port 6I in the main slide valve is opened to valve chamber i5 which permits fluid under pressure to ovv from said valve chamber and the quick action chamber Iii to passage 52 and thence to the vent valve piston chamber 5I.`

This supply of iluid under pressure to the vent valve piston chamber di so exceeds the venting capacity of the timing port 54 through the piston 4I and of the leakage groove 55 around said piston that a suicient pressure is promptly attained on said piston to kmove the vent valve 42 away from seat rib 48 against the opposing pressure of uid and of spring 47 in chamber 44. With the vent valve 42 unseated, fluid under pressure is suddenly vented from the brake pipe iii through pipe i), passages I4, I3', 45, and 45, chambers 44 and 49 and thence to the atmosphere thro-ugh passage 54. rihe resultant sudden reduction in brake pipe pressure in the emergency piston chamber I 2 increases the differential of pressures on the emergency piston I i to a degree sufficient for causing said piston to move'the main slide valve i3 to a position defined by engagement of said piston with a gasket 62.

In this position of the main slide valve I8, a cavity 63 therein connects the emergency reservoir passage 39 to a passage 64 which leads to the brake cylinder pipe I, so that iluid under pressure then flows from the emergency reservoir 6 to the brake cylinder device 8 and equalizes therein to provide high emergency brake cylinder pressure and thereby. an emergency application on the brakes. y

In this position of the emergency slide valve I8 passage 52 is opened past the left-hand end of said slide valve directly to the valve chamber 'i5 so that the supply `of fluid from the valve chamber I5 and quick action chamber I S to the vent valve piston chamber 5I is maintained.

When the vent valve 42 is unseated by piston SI said piston is moved into sealing engagement with a gasket 65 so as to prevent leakage of luid under pressure around said piston from chamber 5! to chamber 53. As a result, the fluid under pressure supplied to chamber 5I is permitted to gradually reduce by iiow throughl the timing port 54 to chamber 53 and thence to the atmosphere through passage 50.

VThe sie of the timing port 54 is so related to the volumes of the valve chamber I5 and quick action chamber I5 that the supply of iiuid from said chambers Will act to hold the vent valve piston 4I in the position in which the ventvalve 42 is unseated for a period of time sufficient tov insure substantially complete venting of fluid under pressure from the brake pipe IG. y

When the pressure of fluid in chamber 5I becomes sufficiently reduced to be overcome by the opposing pressure of spring 47, said spring acts to seat the vent valve 42 and return the piston 4I to its normal position, so that, when desired,

the pressure in brake pipe IQ may be increased for effecting a release of brakesv and for recharging the brake equipment, which will now be described.

When it is desired to effect a release of an emergency application of brakes, fluid under pressure is supplied to brake pipe Ill and thence iows to piston chamber I2. It is customary in charging the brake pipe to initially supply fluid at the high pressure in the usual main reservoir (not shown) provided on the locomotive directly to the brake pipe, and then after a certain lapse of time to supply fluid at a reduced pressure supplied by the usual feed valve device (not shown) to the brake pipe.

'Ihe initial supply of fluid at high pressure to thebrake pipe I causes a rapid increase in pressure in the emergency piston chamber I2 which moves the emergency piston II and thereby the slide valves I8 and I9 back to their normal position shown in the drawing. In this position of piston I I fluid under pressure supplied to chamber I2 flows through the feed port 5l to chambers I5 and I6, but this feed port is so restricted with respect to the initial rapid increase in brake pipe pres-v sure that the differential of pressures on the piston II increases to a degree which overcomes the pressure of spring 29 on the stop 28, whereupon the piston moves the slide valves i8 and Ie further toward the left-hand to a back dump position, as dened by engagement between the left-hand face of said vpiston and the casing.

In this back dump position cavity 63 in the main slide valve I8 connects the brake cylinder passage 64 to a passage 55 so that fluid under pressure then flows Vfrom the brake cylinder device 8 to passage 66 and thence past two serially arranged check valves 67 and 58, through a passage 69 to passage 45 and thence through passage d6, I3, |41, and pipe 9 to the brake pipe IQ.

This back dumping of fluid under pressure from the brake cylinder device 8 to the brake pipe I effects a sudden local increase in brake pipe pressure to provide a suiicient increase in the brake pipe pressure on the next carin a train to effect back dump operation of the emergency valve device on'that car, In this manner the emergency valve devices throughout a train operate serially to provide a material increase in brake pipe pressure.

In the back dump position of the emergency valve device fluidl supplied from the brake pipe to piston chamber I2 continues to ow through port 51 to the valve chamber I5 and quick action chamber It. When the pressure of iluid in these chambers is thus increased sumciently, the pressureof spring 29 on the movable stop 28 returns the piston II and slide valves I8 and I9 to their normal position shown in the drawing, in which position said chambers continue to charge through vthe feed port 5'! until the pressure therein equalizes withthat in the brake pipe.

In case the chambers I5 and i6 tend to become charged to a pressure higher than normally carried in the braise pipe I0, as may occur when fluid at the .highpesssure in the main reservoir on the locomotire is supplied to the brake pipe fory too long a period of time, two serially arranged check valves 'I0 and II will .unseat to permit flow of uid from said chambers to passage 40 and thence to the emergency reservoir 6 which will be at a lower pressure at this time and which is also of relatively large volume and therefore capable to receive any excess pressure attained in said chambers which are of relatively small volume.

As above described, when the static frictional condition of the emergency piston II and auxiliary slide valve I9 is substantially normal, about a five-tenths pound per square inch diierential in pressures is required on said piston to move same and the graduating valve out of their normal positions to service position. Another seven-tenths pounds per square inch differential is then required on the piston to compress the stabilizing spring 24 and permit movement of the graduating valve to emergency position, or in other words, about a one and two-tenths pounds per square inch differential is normally required on said piston to move these parts to emergency position. The emergency valve device will usually operate as intended, as above described, upon a service reduction in brake pipe pressure when the differential required to move the piston and auxiliary slide valve does not exceed the one and two-tenths pounds per square inch just mentioned, but when greater, or in case the kinetic friction of the parts remains sufciently low with a relatively great increase in static resistance to movement, undesired movement of these parts through service position to emergency position may occur upon a service reduction in brake pipe pressure, and as a result an undesired emergency application of brakes on a train would be effected.

In order to prevent undesired emergency operation of the emergency valve devicev upon a service reduction in brake pipe pressure, due to a greater than normal static resistance to movement of the emergency piston and auxiliary slide valve out of their normal release positions, I provide an arrangement which acts on the emergency piston tending to urge same to service position with a force which preferably is just less than sufficient to overcome the normal static resistance to movement of the piston and auxiliary slide valve and thus arranged to off-set any ordinary increase in friction of said piston and valve dueto the accumulations of foreign matter, lack of lubrication, use of improper lubricants or the like.

This arrangement comprises two permanently magnetized elements or magnets 'I2 and 13 arranged with like poles adjacent each other so as to provide a force urging or repelling one from the other. The magnet 'I2 I mount in any suitable part of the emergency valve device, such as the movable stop 28, the position of which remains fixed While e'ecting an application of brakes. rIhe other magnet 'I3 I mount preferably in theend of the emergency piston stem 2U vin alignment with the magnet 'I2 and in such a manner as to be spaced from the latter a slight distance, such as one sixty-fourth of an inch, when the parts of the emergency valve device are in their normal release positions as shown in the drawing.

These magnets may be so designed that with this gap between them, a force will be exerted on the emergency piston I I uring same in the direction of service position equal to for instance four-tenths of a pound per square inch diierential of fluid pressures on said piston. This force is therefore slightly less than required to overcome the normal static resistance to movement of the piston and auxiliary slide valve so as not to interfere with the operation thereof when their frictional characteristics are normal.

However, if the frictional resistance of the piston and auxiliary slide valve increases to a degree above normal the repelling force of magnet 'I2 on magnet 13 will oli-set such increase up to the degree of such force. As above mentioned, if the frictional characteristics of the piston and auxiliary slide valve become changed in service to any extent which requires a diierential in iluid pressures on the piston which exceeds one and two-tenths pounds per square inch to start the piston moving toward service an undesired emergency application of brakes may occur. However with magnets 12, 'I3 producing a force equal to four-tenths of a pound per square inch differential in iiuid pressures on the piston, the diierential in uid pressures required on the piston to start it moving, under this frictional condition, need therefore only be eight-tenths of a pound per square inch. 'Ihis magnetic repelling force then quickly reduces and substantially disappears with a slight increase in the gap or distance between the two magnets, so that the force which continues movement of the piston after it is once started will be promptly reduced to only the eight-tenths of a pound differential in iluid pressures on the piston.

The magnets thus provide a force which merely acts to get the piston started out of release position and then promptly reduces to a negligible degree so that the action of the stabilizing spring and the venting of uid under pressure from the quick action chamber as above described will be effective to stop the piston and auxiliary slide valve in the service position against the remaining eight-tenths pound diiferential in fluid pressure on the piston, which differential is even less than the heretofore permissible value.

It will thus be seen that by the use of the inl vention undesired emergency operation of the valve device is no more likely to occur if the static resistance to movement of the piston and s slide valve I9 is such as to require a one and six-tenths pounds diierential of fluid pressures on the piston to start the piston moving than if a one and two-tenths pounds dierential is required on the piston to start it moving without the use of the magnets.

It will further be seen that if the static resistance to movement of the piston and auxiliary slide valve 'out of release position is such as to require a diierential of fluid pressures of any degree less than the one and six-tenths pounds per square inch the repelling action of the magnets will cause more prompt response of the emergency valve device to a service reduction in brake pipe pressure as Well as to an emergency reduction in brake pipe pressure. This quicker response to a service reduction in brakepipe pressure is of no material consequence, but the quicker response to an emergency reduction in brake pipe pressure will provide quicker operation of the quick action piston 4I and brake pipe vent valve 42 and thereby a quicker emergency application of brakes on the car and a faster serial propagation of the emergency reduction in brake pipe pressure through a train, as is very desirable.

If the static frictional condition of the emergency piston and auxiliary slide should be such as to require a force for overcoming same equal tothe repelling force of magnet I2 and "'13, it Will be seen that the piston will operate upon a very slight reduction in brake pipe pressure andv this will be satisfactory, but if such force is less than the repelling force of the magnets such repelling force will tend to move the piston II and auxiliary slide valve in the direction of their service positions without any reduction in brake pipe-pressure. This latter condition will `not however result in any undesired brake operation since the movement of piston II under the actionof the repelling force of the two magnets will merely close the charging port 5l for valve chamber iii and quick action chamber I6 and open the vent from said chambers through the port 5S in the auxiliary slide valve and port 59y in the main slide valve. A slight venting of fluid underv pressure from these chambers will thenv occur until the pressure in the chambers is reduced suii'iciently below brake pipe pressure on the opposite side of the piston for the piston to move in the direction of its release position against the repelling force. This movement will close the vent from the valve chamber I5 and reopen the charging port 5l. The valve chamber I5 and quick action section chamber It will then recharge with iiuid under pressure from the brake pipe and the piston II and auxiliary slide valve I9 may then move again to service position and eiect further venting of fluid under pressure from these chambers. In other words, with this low static rictional condition, the piston Il and auxiliary slide valve I9 may move back and forth between release and service positions, without however eiectng any undesired brake operation.

As a furtherance of the invention a permanent magnet I4 may be applied to the end of the main slide valve I8 adjacent the movable stop 28 and an opposing permanent magnet 'I7 may be applied to said stop, in order to provide a force on the main slide valve I8 when in its release position to oli-set a certain degree of static friction of said valve and thereby provide :forV quicker movement of said valve upon an emergency reduction in brake pipe pressure and as a result, attain an application of the brakes on aY car quicker than otherwise could be obtained.

With the main slide valve I8 in its release position shown in the drawing, only a relatively small gap is provided between the magnets 'I4 and 'I1 so as tothereby attain the desired repelling force for urging the main slide valve I8 in the direction of piston II. The gap between the magnets 'I4 and 'Il will increase upon movement of the slide valve Il! so that the magnets are thus operative only to aid the piston II in starting the slide valve I8 against static friction, since a slight movement of the slide valve will increase the' gap between the magnets to a degree Where the repelling forces between the magnets substantially disappears.

The degree of repelling force applied by the magnets 'I4 andr 'II to the main slide valve I8 is less' than the minimum force ever required to cause movementv of said valve in order to insure that the valve Will remain in its release position shown at all times except when an emergency application of brakes is desired. y A

It will now be seen that the desirabler resul from use of magnetsV 'I4 and 'I'I in conjunction with the `improvements resulting from use of magnets 'l2 and 'I3 will provide for quicker' stopping Aof a train in an emefgeny, as is very desirable.

If, desired, the magnets 12 and 1.1 mightY constitute two spacedl or opposite portions of a single magnet of ring form encircling theend of the piston stem 20 and. secured in the movable stop 28, as shown in the drawing.

Summary From the above description it will now be seen that I have provided means in the form of -two opposing permanent magnets arranged to offset a certain degree of static friction of a slide valve and/or piston so that for a certain frictional condition, the slide valve and/or piston will be capable of movement by a lesser differential in fluid pressures on the piston than otherwise would be necessary to start the parts moving. Once moving however the piston will usually be able to maintain such movement under the differential of fluid pressures alone, due to the lower kinetic friction of the parts. Thus the magnets are effective merely to start movement, and their eiect quickly disappears upon slight separation of the magnets.

The use of magnets in connection with an emergency piston` and graduating valve thus assures proper operation thereof upon a service reduction in brake pipe pressure under abnormal static frictional conditions, and regardless of the frictional condition of these parts provides for quicker operation ofthe brake pipe vent valve on a car and thereby faster serial transmission of emergency action through a train.

The invention as applied to the main slide valve I8 of the emergency valve device provides for attaining a quicker emergency application of brakes on a car and this in conjunction with the faster serial transmission of emergency action through a train dueto action of magnets 12 and 13, provides for obtaining a quicker application of brakes on all cars oi a train in response to an` emergency reduction in brake pipe pressure and thereby quicker stoppingof the train than. couldv otherwise be attained in an emergency.

Having now described my invention, 'what I` claim as new and desire to secure by LettersPatent is:

l 1. In combination, a slide valve, a movable abutment connected to said valve and subject on4 opposite faces to pressure of fluid and operative to move said valve-upon creation of a dilerential between thev iiuid pressures on said opposite faces, a relatively iXed magnet, and a magnetl arranged in` opposing, relation to said xed mag.- net and associated with said slide valve to provide a force which coacts with said differential.v

to move said slide valve.

2. In combination, a slide valve, a piston connected to said slide valve and subject on opposite faces to pressure of fluid and adaptedy to bev operated upon a differential between such pressures to move said slide valve in one direction, a

relatively fixed permanent magnet, a permanentV with said piston in cooperative and opposing `re-` lation to said xed magnet, the repelling force between saidfmagnets cooperating with the differential of huid-pressures on said piston for moving saidpiston and slidevalve and said repelling force being-less than` the force required to overcome the normal static friction of said piston and slide valve.

4'., In a fluid pressure brake in combination, a brake pipe, a-slidevvalve, apiston subject to the opposing pressuresof said brake pipeand a chamber, a stem connecting said piston and slide valve formovingsaid slide valve with said piston, said piston being arranged to operate upon a reduction inV brake vpipe pressure to move' said slide valvefrom a normal position, a relatively iixed permanent magnet, and a permanent magnet associated with saidpiston stem in cooperativeandopposing relation' to said fixed permanentmagnet to provide a repelling force between said-magnets'which coacts'with the differential in fluid pressures on said piston created by'a reduction in brake pipe pressure to move said pistonand slide valve.

5. In a iiuid pressure brake, in combination, aY brake pipe, a piston subject to the opposing pressures of said brake pipe and a chamber; a slide'valve connected to said piston and arranged to be moved from a normal position by said piston upon a reduction in brake pipe pressure to a degreeV below the pressure of fluid in said chamber, a permanent magnet movable with said slide valve, and a relatively ixed permanent magnet' arranged in cooperative relation with the movable magnet said magnets having like poles adjacent each other to provide a repelling force on said' slide valve for cooperating with a differentiall in fluid pressures created on said piston upon a reduction in brake pipe pressure to move said piston and slide valve out of its normal position.

6. In a fluid pressure brake in combination, a brake pipe, a piston subject to the opposing pressures of said brake pipe and a chamber, a slide valve in said chamber, a piston stem connecting said piston to said slide valve for rendering said piston operable to move said slide valve uponA a reduction in pressure in said brake pipe to a degree below that inr said chamber, a permanent magnet carried by said piston stern, a relatively fixed permanent magnet arranged in opposingv relation to the first named magnet, the repelling forces between said magnetsacting on said stem for cooperation with the differential in fluid.

pressures created on said piston upon a reduction 1n brake pipe pressure tomo-ve said slide valve.

'l'. In a uid pressure brake, inil combination, a`

brak'epipeVa valve device comprising a casing, a

piston insaid casing subject to the opposing pres-- suresof` the vbrake pipe and a chamber, a main.

slide valve in-said chamber, an auxiliary slide valve in. said chamber mounted .to slide on' said main slidevalve, a stem extending from said piston linto said-chamber and connected to said slide valves.said piston being operative upon a reduction inbrake pipe pressure to a degree below that in said'V valve chamber toA first move said auxiliary slide valvel relative to said main slide valve and to' then move saidmain slide valve, a relatively fixedV permanent magnet in said casing, and a permanentl magnet associated with said piston in opposing relation to said xed magnet. providingaforce on saidpiston arranged to cooperate with'` azdifierentialinfluid pressuresy thereon created-by a'reductionvin; brake. pipe pressure for moving said piston and auxiliary slide valve relative to said main slide valve.

8. In a fluid pressure brake, in combination, a brake pipe, a valve device comprising a casing, a piston in said casing subject to the opposing pressures of the brake pipe and a chamber, a main slide valve in said chamber, an auxiliary slide valve in said chamber mounted to slide on said main slide valve, a stem extending from said piston into said chamber and connected to said slide valve, said piston being operative upon a reduction in brake pipe pressure to a degree below that in said valve chamber to rst move said auxiliary slide Valve relative to said main slide valve and to then move said main slide valve, a relatively fixed permanent magnet in said casing, a permanent magnet associated with said piston in opposing relation to said fixed magnet providing a force on said piston arranged to cooperate With a differential in iluid pressures thereon created by a reduction in brake pipe pressure for moving said piston and auxiliary slide valve relative to said main slide valve, a third permanent magnet having a relatively fixed position in said casing, and a fourth permanent magnet associated with said main slide valve and cooperative with said third magnet to provide a repelling force which acts on said main slide valve for cooperating with the differential in pressures created on said piston upon a reduction in brake pipe pressure for moving said main slide valve.

9. In a luid pressure brake in combination, a brake pipe, a piston subject to the opposing pressures of said brake pipe and in a chamber, a main slide Valve, an auxiliary slide valve mounted to slide on said main slide valve, a stem projecting from said piston into said chamber and having connections with said slide valves for moving said auxiliary slide valve from a normal position relative to said main slide valve and for then moving said main slide valve from a normal position upon a reduction in brake pipe pressure on said piston, said piston being operative upon an increase in brake pipe pressure at a certain rate to move said slide valves back to said normal position and at a faster rate past said normal position to an inner position, a member engaging said stem in said normal position of said valves, and movable by said stem to an inner position upon movement of said valves to their inner position, a spring acting on said member for opposing movement thereof and thereby of said piston and said valves to said inner position and for returning said piston and valves to their normal positions, a permanent magnet carried by said member, and another permanent magnet carried by said piston stern, said magnets being arranged to repell each other for providing a force on said piston to cooperate with the diierential in uid pressures created thereon upon a reduction in brake pipe pressure to actuate said piston for moving said auxiliary slide valve relative to said main slide valve.

10. In a luid pressure brake in combination, a brake pipe, a piston subject to the opposing pressures of said brake pipe and in a chamber, a

main slide valve, an auxiliary slide valve mounted to slide on said main slide valve, a stem projecting from said piston into said chamber and having connections with said slide valves for moving said auxiliary slide valve from a normal position relative to said main slide valve and for then moving said main slide valve from a normal position upon a reduction in brake pipe pressure on said piston, said piston being operative upon an increase in brake pipe pressure at a certain rate to move said slide valves back to said normal position and at a faster rate past Said normal position to an inner position, a member engaging said stem in said normal position of said valves and movable by said stem to an inner position upon movement of said valves to their inner position, a spring acting on said member for opposing movement thereof and thereby of said piston and said Valves to said inner position and for returning said piston and valves to theil` normal positions, a permanent magnet carried by said member, another permanent magnet carried by said piston stem, said magnets being arranged to repell each other for providing a force on said piston to cooperate with the differential in fluid pressures created thereon upon a reduction in brake pipe pressure to actuate said piston for moving said auxiliary slide valve relative to said main slide valve, a third permanent magnet carried by said member, and a fourth permanent magnet carried by said main slide valve said third and fourth permanent magnets being arranged to provide a repelling force which acts on said main slide valve to cooperate with the diierential in uid pressures provided on said piston for moving said main slide valve out of normal position.

PHILIP L. CRIT'I'ENDEN. 

